jpegpixi: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/jpegpixi - from package: jpegpixi

You may install the required package with command apt-get install {package}

Error in other languages:
jpegpixi: bevel nie gevind nie
jpegpixi: comandă negăsită
jpegpixi: comando não encontrado
jpegpixi: commande introuvable
jpegpixi: command not found
jpegpixi: käsku ei ole
jpegpixi: không tìm thấy lệnh
jpegpixi: komanda nerasta
jpegpixi: Kommando nicht gefunden.
jpegpixi: kommandot finns inte
jpegpixi: komut yok
jpegpixi: nie znaleziono polecenia
jpegpixi: níor aimsíodh an t-ordú
jpegpixi: no se encontró la orden
jpegpixi: no s'ha trobat l'ordre
jpegpixi: opdracht niet gevonden
jpegpixi: parancs nem található
jpegpixi: perintah tidak ditemukan
jpegpixi: príkaz nenájdený
jpegpixi: příkaz nenalezen
jpegpixi: команда не найдена
jpegpixi: командата не е открита
jpegpixi: 命令找不到
jpegpixi: コマンドが見つかりません